Checking the Back Forty Volume 2 Issue 3 – May 29, 2012

Kevin H. Ganoe, Regional Field Crop Specialist, Central New York Dairy & Field Crops Team, Cornell Cooperative Extension of Chenango, Herkimer, Otsego,and Schoharie Counties

Weather Data for Week Ending Sunday, May 27, 2012
No doubt no two years are alike and certainly 2012 is living up to the tradition. The 2012 growing season started with May temperatures in mid March and deep freezes in April. Table 1 below has Growing Degree Days (GDD) at 2 week intervals since the first corn was planted the week of April 23. Table 2 is the rainfall since April 1.

Table 1. Growing Degree Days

The 2012 season continues with GDDs ahead and though since April 1 for the most part we are rainfall ahead, we have had weeks such as the past week where rainfall was behind. Remember corn needs about 110 GDDs from planting to germination with soybeans needing similar heat units.

Table 2. Rainfall Data (From the USDA National Agricultural Statistics Service New York Field Office and the New York Department of Agriculture and Markets 1/ Season accumulations are for April 1st to date. Weekly accumulations are through 7:00 AM Sunday Morning)

Right now early planted corn is in the 4-5 leaf stage. Corn should be sidedressed with nitrogen at the V6 stage. Looking ahead it should take 1250 GDDs for 96-100 RM hybrids and 1300 GDDs for 101-105 RM hybrids to reach tasseling/silking.

Potato Leafhopper Present
We are starting to find Potato Leafhoppers (PLH) present in new seedings and in second cutting alfalfa. Yesterday we were in second cutting alfalfa stands 6-7 inches tall that were over threshold and should be controlled with in-secticide. Harvest is always a good control meth-od if there is enough alfalfa present to harvest. PLH will move on to fields with newer growth. New seedings should receive some special atten-tion as there always seems to be enough leaves left on the young plants that harvest does not al-ways drive the PLH away. Check all regrowth, new seeding or established stands, after harvest with a sweep net for the presence of these in-sects. To determine economic thresholds use the table below from the 2012 Cornell Guide for Inte-grated Field Crop Management (http://ipmguidelines.org/FieldCrops/Chapters/CH04/CH04-10.aspx).

Economic Threshold for Potato Leafhopper (http://ipmguidelines.org/FieldCrops/Chapters/CH04/CH04-10.aspx)

Using a 15 inch sweep net and using 10 sweeps at 5 locations in a field determine the number the average number of PLH per sweep. Get the height of your alfalfa and look at the table above to determine if your average number of PLH per sweep is greater than the economic threshold indicated above. If it is above the threshold treatment or harvest is warranted.

Counting on a post-emergence weed control program in corn: NOW is the time!
With many things to do in the field this time of year you may be planning on a post emergence herbicide program for your corn but time has slipped by without it. Check your fields now to see if weed and corn height is appropriate for the herbicides you have se-lected. You might find given the good growing condi-tions weeds and corn have progressed faster than you would have thought. Post-emergence herbicides can provide good control of weeds but if delayed can cause yield losses from weed competition.

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